A Coefficient of Thermal Expansion (CTE) of an epoxy resin is about 50 ppm/° C. to 80 ppm/° C., a significantly higher several to tens of times than that of a ceramic and a metal (for example, a CTE of silicon is 3 ppm/° C. to 5 ppm/° C., and a CTE of copper is 17 ppm/° C.). Thus, for example, in a case in which an epoxy resin is used in conjunction with an inorganic material or a metallic material in the field of semiconductors, displays, and the like, designing and processing of a component may have significant limitations due to CTE-mismatch. In addition, in the case of semiconductor packaging, for example, a silicon wafer and an epoxy substrate may be adjacent to each other, or in a case of a coating in which a polymer film is coated with an inorganic barrier to impart gas barrier properties, the defects such as the crack formation in an inorganic layer, warpage of a substrate, peeling of a coating layer, breakage of a substrate, and the like may occur due to a CTE-mismatch between materials.
Because of a high CTE of an epoxy resin and a subsequently the high dimensional change, the development of technologies such as next generation semiconductor substrates, printed circuit boards (PCB), packaging, organic thin film transistors (OTFT), flexible display substrates, and the like may be limited. Particularly, recently, in the semiconductor and PCB industry, due to an epoxy with a significantly high CTE in comparison with metallic/ceramic materials, the design of next generation components requiring high levels of integration, miniaturization, flexibility, performance, and the like is somewhat challenging.
So far, to improve thermal expansion properties of an epoxy resin (in other words, to achieve a low CTE), generally, (1) a method of making a composite of an epoxy resin with inorganic particles (inorganic filler) and/or a glass fiber, or (2) a method of designing a novel epoxy resin with a decreased CTE have been used.
In a case in which an epoxy resin makes composite with inorganic particles as a filler to improve thermal expansion properties, a large amount of silica inorganic particles having a size of about 2 μm to 30 μm is required to obtain a reduction in a CTE. However, a problem of the decreased processability accompanies due to the inclusion of a large amount of inorganic particles. In other words, a problem such as a decrease in fluidity, a formation of a void when a narrow gap is filled, and the like, may occur due to a large amount of inorganic particles. In addition, even in the case that a CTE of an epoxy composite including a glass fiber is significantly reduced, the CTE thereof may be still be relatively high in comparison with that of a silicon chip, or the like.
As described above, due to limitations of the current epoxy composite technology, manufacturing of highly integrated and high performance electronic components such as next generation semiconductor substrates, PCBs, and the like may be limited. Thus, to overcome challenges such as a high CTE of a thermosetting polymer composite in the related art, a lack of thermal resistance properties and processability due to the high CTE thereof, and the like, the development of an epoxy composite with the improved thermal expansion properties, in other words, low CTE and high glass transition temperature properties, is required.